Conventionally, with a purpose of the effective use of non-petroleum based fuel oil, a method for producing aviation fuel (jet fuel) using a blendstock with a low sulfur content is known.
For example, Japanese Translation of PCT International Application Publication No. 2006-522859 (PTL 1) discloses a method for producing aviation fuel using a low temperature Fischer Tropsch raw material. Specifically, it is a method for producing low sulfur synthesis diesel fuel and low soot and smoke emitting aviation fuel from a low temperature Fischer Tropsch (LTFT) raw material, for producing a light kerosene fraction capable of being used as low soot and smoke emitting aviation fuel and/or aviation fuel blend stock, and a heavy diesel fraction capable of being used as low sulfur synthesis diesel fuel and/or diesel fuel blend stock, including rectification of a low temperature Fischer Tropsch raw material into a light kerosene fraction and a heavy diesel fraction with a volume ratio of 1:2 to 5:4, wherein the fractions substantially meet diesel fuel and aviation fuel standards.
However, when jet fuel with a low sulfur content is produced using Fischer Tropsch synthesis oil (hereinafter, referred to as “FT synthesis oil”), since the FT synthesis oil is paraffinic, the FT synthesis oil is required to be hydrogenation transformed to have sufficient quality to be used as jet fuel. This is because the freezing point is high when it remains paraffinic, and it cannot be applied to jet fuel requiring a low freezing point, so a step of conducting hydroconversion hydrogenation transformation treatment (hereinafter, referred to as “hydrogenation treatment”) to lower the freezing point of the FT synthesis oil is required. In addition, the hydrogenation treatment of the invention includes, for example, hydroisomerization and hydrocracking.
When quality improvement (e.g., decrease in the freezing point) of the produced jet fuel blendstock is attempted by the FT synthesis oil hydrogenation treatment described above, since quality improvement and yield increase of the jet fuel blendstock are in the relationship of trade off, there has been a problem in that the yield of the jet fuel blendstock obtained with respect to the amount of FT synthesis oil decreases. Therefore, development of a technique capable of producing a jet fuel blendstock derived from FT synthesis oil at a good yield, and also producing jet fuel with a sufficiently good quality (e.g., meeting jet fuel standards) using the jet fuel blendstock derived from FT synthesis oil has been desired.